One set of techniques to maximize hydrocarbon production is referred to as “stimulation.” Stimulation procedures are usually performed on production wells completed in oil and/or gas containing formations; however, injection wells used in secondary or tertiary recovery operations can also be fractured to facilitate the injection of the fluids.
One stimulation technique is hydraulic fracturing. Hydraulic fracturing involves injecting a fracturing fluid into the wellbore directed at the face of a hydrocarbon-bearing geologic formation at pressures sufficient to initiate and extend cracks (fractures) in the formation. The continued pumping of the fracturing fluid extends the fractures. A proppant, such as sand or other particulate material, can be suspended in the fracturing fluid and introduced into the created fractures. The proppant material holds or “props” open the fracture and prevents the formed fractures from closing upon reduction of the hydraulic pressure. In this way, conductive channels remain through which produced fluids can readily flow to the wellbore upon completion of the fracturing treatment.
A typical proppant used in hydraulic fracturing is 20/40 mesh sand or bauxite. The shape of the sand is generally rounded or globular, often having jagged or rough surface features, although it can also approach a relatively smooth spheroid shape.
Such globular proppants sometimes flow back into the wellbore during production because the globular shapes slide by each other with relative ease. Proppant flow back is more pronounced when relatively large diameter perforations are used due to the inability of the globular shaped proppants to bridge openings that are substantially larger than the size of the proppant. When proppant material is flowed back from a well, the proppant becomes an undesirable contaminant because the proppant acts to reduce the production of oil from the well by clogging the wellbore. These proppants also must be separated from the oil to render the oil commercially useful, adding more expense and effort to oil processing.
One approach used to combat the problem of proppant flow back has been to mix fibrous materials in intimate contact with the proppant particles. The fibers are placed in the wellbore and believed to form a net across constructions and orifices in the proppant pack, thereby attempting to stabilize the proppant pack. The fibers form a net by merely tangling or wrapping around or crossing each other. The fibers are only able to hold minimal tensile load, however. Thus, any load other than a minimal tensile load will result in detangling and buckling of the fibers, which provides for inefficient control of flow back.
Other particulate materials besides proppants can also flow back from the well, such as particulates and fines from the formation. Undesirable flow back of particulate materials during production of oil or other fluids from a subterranean formation can pose a serious problem. This problem is particularly pronounced in unconsolidated formations, which are those that are less structured, and therefore, more easily facilitate the uninhibited flow of particulate materials. Such particulate materials that become contaminants when flow up the wellbore significantly wear down well production equipment, including the pumps and seals used in the recovery and pumping process.
Thus, there has been a long-felt need in the field for a proppant and method that can reduce or eliminate proppant and particle flow back.